Aug 28 (Reuters) - JPMorgan Chase & Co is
investigating a possible cyber attack and working with law
enforcement authorities to determine the scope, a company
spokeswoman said on Thursday morning.

The bank was taking additional steps to safeguard sensitive
or confidential information, though it did not see unusual fraud
activity at this time, company spokeswoman Trish Wexler said.

JPMorgan disclosed the investigation after the FBI said
Wednesday evening it was investigating media reports earlier in
the day that several U.S. financial companies have been victims
of recent cyber attacks.

"We are working with the United States Secret Service to
determine the scope of recently reported cyber attacks against
several American financial institutions," FBI spokesman Joshua
Campbell said in a statement late Wednesday.

Campbell did not name any companies or give more details,
although media reports had named JPMorgan as one victim of the
attacks. Other potential victims have yet to be named.

Officials with the Secret Service could not be reached for
comment.

JPMorgan launched its investigation after malicious software
was recently discovered in the bank's network, signaling it was
the victim of a cyber attack, two people familiar with the
incident told Reuters. The bank has yet to determine the
severity, said the sources, who asked not to be identified
because they were not authorized to speak publicly about the
matter.

Bloomberg News reported Wednesday that Russian hackers were
believed to have carried out cyber attacks against JPMorgan and
another unnamed U.S. bank in mid-August, resulting in the loss
of sensitive data. Authorities were investigating whether the
breaches were linked to recent attacks on major European banks,
Bloomberg reported.

The New York Times reported late Wednesday the networks of
JPMorgan and at least four other U.S. banks had been infiltrated
in a string of coordinated attacks this month, citing four
people familiar with the investigation.

The attackers stole large quantities of data, including
checking and savings account information, though their
motivation was not yet clear, the Times reported, adding that
several private security firms were hired to conduct forensic
reviews of infected networks.

Reuters was not able to independently verify the details in
the Bloomberg and Times reports.
(Reporting by Jim Finkle in Boston and David Henry in New York;
Additional reporting by Mark Hosenball and Doina Chiacu in
Washington; Editing by David Gregorio, Jeremy Laurence and
Jeffrey Benkoe)